The use of frac balls to control fluid flow in a subterranean well is well known. The frac balls are generally dropped or injected into a well stimulation fluid stream being pumped into the well. This can be accomplished manually, but the manual process is time consuming and requires that workmen be in close proximity to highly pressurized frac fluid lines, which is a safety hazard. Consequently, frac ball droppers or injectors have been invented to permit faster and safer operation.
As is well understood in the art, multi-stage well stimulation operations often require that frac balls of different diameters be sequentially injected into the well in a predetermined size order that is graduated from a smallest frac ball to a largest frac ball. While frac ball injectors are available that can be used to inject single frac balls in any size order, such frac ball injectors require that a plurality of injector spools be vertically stacked to provide the required availability of frac balls of different diameters. The stacking of injector spools increases weight on the wellhead and raises working height, both of which are undesirable.
There therefore exists a need for a frac ball injector for use during well completion, re-completion or workover operations that does not raise working height or place extra weight on a wellhead.